The positive mindset must go with the skill games. When you have the positive mindset, you also apply your skills in the game to win the game. And the games you apply your skills and strategies are poker an sport games and other casino games are not skills but lucky games.
And I don't think any gambler visit the casino with a negative mindset. Everyone comes with positive mindset but not all wins. Positive mindset also goes with luck as well.
You're right every gambler that is coming to gamble has a mindset that is positive driven as the wise of anyone gambling is to win money but gambling doesn't work that way it's not about having a positive mindset when it comes to gambling winning on gambling is luck and not only limited to having a positive mindset only